For many plant species there has been determined a relationship between plant populations or densities on a given area and the resulting yields. Overcrowding reduces yield due to excessive competition between plants for light, moisture and nutrients as well as increasing risk of disease due to inadequate ventilation. Underpopulating reduces yield due to unused or wasted potential cropping area. This relationship applies to most crops. However in this document an illustrative reference will be made to one type of cereal crop-wheat. This is by way of example and is not limiting.
The sowing operation is very important in determining the yield of a particular crop. Most seeding apparatuses used in broad acre wheat cropping use a “sprinkle” technique to generally toss seeds in rows about 150 millimeters or more apart. These seeds are initially metered out using rollers or various shaped gears adjusted to give selected flow rates. Pneumatic systems can be used to carry the seeds through a system of pipes to divider heads which separate the seeds into multiple elongated channels that can extend laterally away from the seeder over a number of rows where it is allowed to sprinkle into the row.
Usually the seeding rate is determined by the seed flow rate from the apparatus however this is an average flow rate. It can be seen that although in this sprinkling there might have been some initial metering this becomes only an average metering at the various outlets. Further the drop from a channel outlet can result in its own variation of placement.
This result might seem to fulfill the required distribution to produce a maximum yield on the macro level but due to the affect of overpopulation and underpopulation on the micro level the average macro distribution of seed does not result in maximum yield. The overall result is that there can be 50% or more of the seeds in an overpopulated or underpopulated arrangement on the micro level although the average might be near the required. Each patch of overpopulated or underpopulated seeds is a micro growing location with its deficits because of the immediate vicinity and is not particularly compensated by the average macro location population density.
Less competition from neighbours for root space, nutrients, moisture and light all contribute to an increase in yield made possible through vigorous early growth of seedlings in the crop establishment phase. This results in earlier ground cover with the shading by crop leaves slowing soil moisture loss from sun and wind as well as smothering weed development. All these factors are known to dramatically assist yields. However on the micro level if there is overpopulation there is over competition resulting in a decrease of yield. Further there is increased risk of disease from insufficient ventilation. Alternatively if the spacing is considerable there is space for weeds to establish or open areas which are unproductive and which increase the likelihood of drying out the soil. Therefore it is the balance and correct spacing on the micro level which is required for maximum yields. To this end the overall percentage of overpopulated and underpopulated sowing must be substantially reduced.
There are a range of known sowing apparatuses in use at present. Some of these use vacuum systems to pick up seeds and to break the vacuum to release the seed for planting. Disc and drum vacuum planters are two types of vacuum systems.
A disc system is shown in U.S. Pat. No 4,469,244 which discloses a suction-type distributor for a single-seed seeder with a rotary apertured disk. The distributor includes an aperture disk rotating in a casing and two adjoining selector plates pivoted from the casing and provided with alternate projections spaced on their edges extending around the path of apertures on the disk so as to straddle said path. The relative angular position of the two plates are adjustable by means of a single lever provided with cams and pivoted on casing.
A drum system is shown in U.S. Pat. No. 4,306,509 which discloses an apparatus for continuously metering seeds onto a seedbed and simultaneously pressing the seeds into the soil. The seed planting apparatus includes a drum adapted to be moved in rolling contact across the seedbed, and which transports seeds on its peripheral wall from a hopper to the seedbed. The seeds are retained against apertures in the peripheral wall by means of a vacuum transmitted to the apertures through manifolds within the drum that are interconnected with a vacuum pump by means of individual hoses. A cam interrupts the vacuum by compressing the hoses when the seed-bearing apertures contact the seedbed, thereby releasing the seeds and pressing them into the soil. The seeds are preferably placed on the seedbed in a uniformly spaced array predetermined by the uniform alignment and spacing of the apertures on the wall of the drum. An air brush is also included to remove substantially all excess seeds from the apertures before the apertures rotate from beneath the hopper, and a brush removes soil and debris from the exterior wall of the drum before the apertures re-enter the hopper.
Another system is shown in U.S. Pat. No. 6,564,729 which has a vacuum seed metering assembly for evenly distributing seeds from a seed hopper includes a rotating perforated drum and a pair of stationary walls forming a suction area and a release area inside the drum. The suction area is adjacent a seed hopper such that individual seeds are held to apertures in the drum by suction as the apertures pass by the seed hopper. As the drum rotates, each seed is released into an associated distribution tube when the aperture passes into the release area.
A major problem with such systems is they operate at relatively slow speeds, which thereby restricts the machines planting speed. All known vacuum planter apparatuses using rotating drums or discs pick up individual stationary seeds from a pick-up area and rotate the seeds to a spaced drop off location. This can only be achieved at relatively low rotation speeds. At higher speeds the moving drum or disc surface passes the stationary seeds in the pickup zone too quickly to pick up the seed. Therefore the majority of these vacuum planter machines are limited to maximum sowing ground speeds of about 12 to 15 kilometers per hour.
It is therefore a first object of the invention to improve maximum yield by providing a seed distribution method and apparatus which improves the micro growing location by lowering the percentage of overpopulated or underpopulated seed density.
It is a second object of the invention to provide a method of seed distribution and a seeding apparatus, which allows accurate faster seeding than the above conventional means.
It is a third object of the invention to provide a method for the placement of the individual seeds within each row at a selected spacing together with the ability to space multiple rows each at a selected distance apart, both these being variable and easily changed, to provide numerous sowing grid options.
It is a fourth object of the invention to provide an apparatus which can place predominantly individual seeds at considerable speed enabling the rapid sowing of a grid pattern which gives the optimum plant population outcome required for a particular crop.
It is a further object of the invention to provide an improved method of seed distribution and a seeding apparatus, which overcomes or at least ameliorates the problems of the prior art.